Camera and light source synchronization for object tracking

ABSTRACT

Technologies for camera and light source synchronization include an imaging device to detect a current location of an object in a captured image generated by the imaging device. The imaging device predicts a next location of the object in a next captured image, generated by the imaging device, based on the current location of the object. The imaging device determines an illumination interval defining a period of time during which a camera of the imaging device is to expose a set of sensor lines during the capturing of the next captured image and activates a light source of the imaging device to illuminate the object during the determined illumination interval. The set of sensor lines corresponds with the predicted next location of the object.

BACKGROUND

Remote eye and gaze tracking systems have been implemented in variousapplications to track a user's eye movements and/or the direction inwhich the user is looking. The range of such applications extends fromserious (e.g., airport security systems) to playful (e.g., video gameavatar renderings). Typical eye tracking systems may use varioustechnologies to track a user's eye movements. For example, in someimplementations, infrared sensors are used to detect reflections from aperson's retina/cornea.

Digital cameras have become ubiquitous consumer devices, oftenincorporated in other digital electronic devices such as smartphones,tablets, and other computing devices. Typical digital cameras include animage sensor, such as a charge-coupled device (CCD) or a complementarymetal-oxide-semiconductor (CMOS) image sensor, which may be formed by anarray of individual pixel sensors. Depending on the type of digitalcamera, the associated image sensor may be operated in a global shuttermode or a rolling shutter mode. In a global shutter camera, the entirearray of individual pixel sensors exposed and captured during the sametime window. Conversely, in a rolling shutter camera, portions of thearray of pixel sensors are captured at different times. However, becausethe entire image is not captured at the same point in time in a rollingshutter camera, the captured image may be distorted due to variousphenomena. For example, rapid movement or lighting changes may result inartifacts appearing in the generated image. Additionally, the sensorreadout time can be substantially longer than the ideal exposure time.However, rolling shutter cameras oftentimes benefit from improved imagequality and reduced cost relative to global shutter cameras.

In operation, a rolling shutter camera captures images (e.g., as videoframes) by consecutively reading out rows or columns of pixels sensors(“sensor lines”) of the associated image sensor. Each sensor line isread on a sequential, rolling basis. Similarly, the sensor lines arereset on a rolling, sequential basis prior to readout. Specifically,each sensor line is reset (i.e., any stored information is discarded) apredetermined amount of time prior to the readout time for that sensorline such that each sensor line is exposed for the same amount of timefollowing reset. The overall number of sensor lines of a given imagesensor typically defines the resolution of the associated camera (i.e.,a greater number of sensor lines result in a higher resolution image).

BRIEF DESCRIPTION OF THE DRAWINGS

The concepts described herein are illustrated by way of example and notby way of limitation in the accompanying figures. For simplicity andclarity of illustration, elements illustrated in the figures are notnecessarily drawn to scale. Where considered appropriate, referencelabels have been repeated among the figures to indicate corresponding oranalogous elements.

FIG. 1 is a simplified block diagram of at least one embodiment of animaging device having camera and light source synchronization;

FIG. 2 is a simplified block diagram of at least one embodiment of anenvironment of the imaging device of FIG. 1;

FIG. 3 is a simplified flow diagram of at least one embodiment of amethod for performing camera and light source synchronization on theimaging device of FIG. 1;

FIG. 4 is a simplified flow diagram of at least one embodiment of amethod for resetting sensor lines with camera and light sourcesynchronization on the imaging device of FIG. 1;

FIG. 5 is a simplified flow diagram of at least one embodiment of amethod for reading sensor lines with camera and light sourcesynchronization on the imaging device of FIG. 1; and

FIG. 6 is a simplified temporal graph of at least one embodiment ofcamera and light source synchronization on the imaging device of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will be describedherein in detail. It should be understood, however, that there is nointent to limit the concepts of the present disclosure to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives consistent with the presentdisclosure and the appended claims.

References in the specification to “one embodiment,” “an embodiment,”“an illustrative embodiment,” etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may or may not necessarily includethat particular feature, structure, or characteristic. Moreover, suchphrases are not necessarily referring to the same embodiment. Further,when a particular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to effect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described. Additionally, it should be appreciated that itemsincluded in a list in the form of “at least one A, B, and C” can mean(A); (B); (C): (A and B); (B and C); or (A, B, and C). Similarly, itemslisted in the form of “at least one of A, B, or C” can mean (A); (B);(C): (A and B); (B and C); or (A, B, and C).

The disclosed embodiments may be implemented, in some cases, inhardware, firmware, software, or any combination thereof. The disclosedembodiments may also be implemented as instructions carried by or storedon a transitory or non-transitory machine-readable (e.g.,computer-readable) storage medium, which may be read and executed by oneor more processors. A machine-readable storage medium may be embodied asany storage device, mechanism, or other physical structure for storingor transmitting information in a form readable by a machine (e.g., avolatile or non-volatile memory, a media disc, or other media device).

In the drawings, some structural or method features may be shown inspecific arrangements and/or orderings. However, it should beappreciated that such specific arrangements and/or orderings may not berequired. Rather, in some embodiments, such features may be arranged ina different manner and/or order than shown in the illustrative figures.Additionally, the inclusion of a structural or method feature in aparticular figure is not meant to imply that such feature is required inall embodiments and, in some embodiments, may not be included or may becombined with other features.

Referring now to FIG. 1, in the illustrative embodiment, an imagingdevice 100 includes a camera 120 and one or more light sources (e.g.,exposure lights) 122 associated therewith. As discussed in more detailbelow, the camera 120 includes a plurality of sensor lines 130 and isconfigured to operate in a rolling shutter mode. In use, the imagingdevice 100 is configured to synchronize the reading/resetting of thesensor lines 130 of the camera 120 and the activation of the associatedlight sources 122. As discussed in detail below, such synchronizationmay reduce the energy consumption of the imaging device 100 associatedwith activation of the light sources and thereby improve the energyefficiency of the imaging device 100 because the light sources areactivated only for a period required to capture the desired object(e.g., a user's eyes). In some embodiments, synchronization may alsoreduce the incidence of motion blur and other image artifacts and/orimprove image quality at minimal or reduced cost.

The imaging device 100 may be embodied as any type of computing devicecapable of camera and light source synchronization and performing thefunctions described herein. For example, the imaging device 100 may beembodied as a stand-alone digital camera, cellular phone, smartphone,tablet computer, laptop computer, personal digital assistant, mobileInternet device, desktop computer, and/or any othercomputing/communication device. As shown in FIG. 1, the illustrativeimaging device 100 includes a processor 110, an input/output (“I/O”)subsystem 112, a memory 114, a data storage 116, a communicationcircuitry 118, a camera 120, one or more light sources 122, and one ormore peripheral devices 124. Of course, the imaging device 100 mayinclude other or additional components, such as those commonly found ina typical computing device (e.g., various input/output devices), inother embodiments. Additionally, in some embodiments, one or more of theillustrative components may be incorporated in, or otherwise from aportion of, another component. For example, the memory 114, or portionsthereof, may be incorporated in the processor 110 in some embodiments.

The processor 110 may be embodied as any type of processor capable ofperforming the functions described herein. For example, the processormay be embodied as a single or multi-core processor(s), digital signalprocessor, microcontroller, or other processor or processing/controllingcircuit. Similarly, the memory 114 may be embodied as any type ofvolatile or non-volatile memory or data storage capable of performingthe functions described herein. In operation, the memory 114 may storevarious data and software used during operation of the imaging device100 such as operating systems, applications, programs, libraries, anddrivers. The memory 114 is communicatively coupled to the processor 110via the I/O subsystem 112, which may be embodied as circuitry and/orcomponents to facilitate input/output operations with the processor 110,the memory 114, and other components of the imaging device 100. Forexample, the I/O subsystem 112 may be embodied as, or otherwise include,memory controller hubs, input/output control hubs, firmware devices,communication links (i.e., point-to-point links, bus links, wires,cables, light guides, printed circuit board traces, etc.) and/or othercomponents and subsystems to facilitate the input/output operations. Insome embodiments, the I/O subsystem 112 may form a portion of asystem-on-a-chip (SoC) and be incorporated, along with the processor110, the memory 114, and other components of the imaging device 100, ona single integrated circuit chip.

The data storage 116 may be embodied as any type of device or devicesconfigured for short-term or long-term storage of data such as, forexample, memory devices and circuits, memory cards, hard disk drives,solid-state drives, or other data storage devices. The communicationcircuitry 118 may be embodied as any communication circuit, device, orcollection thereof, capable of enabling communications between theimaging device 100 and other remote devices over a network (not shown).To do so, the communication circuitry 118 may use any suitablecommunication technology (e.g., wireless or wired communications) andassociated protocol (e.g., Ethernet, Bluetooth®, Wi-Fi®, WiMAX, etc.) toeffect such communication depending on, for example, the type ofnetwork, which may be embodied as any type of communication networkcapable of facilitating communication between the imaging device 100 andremote devices.

The camera 120 may be embodied as any peripheral or integrated devicesuitable for capturing images, such as a still camera, a video camera, awebcam, or other device capable of capturing video and/or images. Asdiscussed in more detail below, the camera 120 captures images of aobject (e.g., a person's face or eyes) that is to be tracked. Althoughthe illustrative imaging device 100 includes a single camera 120, itshould be appreciated that the imaging device 100 may include multiplecameras 120 in other embodiments, which may be used to capture images ofthe object, for example, from different perspectives. As discussedabove, the camera 120 is illustratively is embodied as a digital cameraconfigured to operate in a rolling shutter mode. In the rolling shuttermode, each sensor line 130 of the camera's 120 field of view may bereset and subsequently exposed for a predetermined amount of time priorto reading the sensor line (for example, see FIG. 6). In addition to thesensor lines 130, the camera 1230 may also include one or more imagingsensors, such as infrared sensors, to capture the images. As discussedbelow, the captured images are analyzed for eye detection and/or gazetracking of a subject in the field of view of the camera 120.

The light source(s) 122 may be embodied as any type of light sourcecapable of illuminating an object being tracked by the imaging device100. For example, in one embodiment, the light sources 122 are embodiedas infrared light sources configured to project infrared light onto thetracked object (e.g., used in conjunction with infrared sensors). Thelight sources 122 may be configured to illuminate the entire scene(i.e., the area within the field of view of the camera 120) or, in otherembodiments, to illuminate only the objects being tracked (e.g., theuser's eyes) or some portion of the scene. Of course, it should beappreciated that the light sources 122 may be dedicated to imageillumination in some embodiments. By illuminating the object beingtracked, the camera 120 may capture a higher quality image than possiblewithout illumination.

The peripheral devices 124 of the imaging device 100 may include anynumber of additional peripheral or interface devices. The particulardevices included in the peripheral devices 124 may depend on, forexample, the type and/or intended use of the imaging device 100. Asshown in FIG. 1, the illustrative peripheral devices 124 include one ormore sensors 132. The sensor(s) 132 may include any number and type ofsensors depending on, for example, the type and/or intended use of theimaging device 100. The sensor(s) 132 may include, for example,proximity sensors, inertial sensors, optical sensors, light sensors,audio sensors, temperature sensors, thermistors, motion sensors, and/orother types of sensors. Of course, the imaging device 100 may alsoinclude components and/or devices configured to facilitate the use ofthe sensor(s) 132. For example, the imaging device 100 may includeinertial sensors to detect and/or track movement of the imaging device100 or a component of the imaging device 100. As discussed below,inertial data may be used by the imaging device 100 to make an improvedestimation of the next location of the object being tracked (e.g., asubject's eyes).

Referring now to FIG. 2, in use, the imaging device 100 establishes anenvironment 200 for camera and light source synchronization. Asdiscussed below, the imaging device 100 may synchronize the resettingand reading of particular sensor lines 130 of the camera 120 with theactivation of the light sources 122. In doing so, the imaging device 100may only activate the light sources 122 when a desired portion of thescene (e.g., the tracked object) is to be captured. For example, thelight sources 122 may be activated when the sensor lines 130corresponding to the desired portion of scene are to be reset and/orread by the camera 120 as discussed in more detail below.

The illustrative environment 200 of the imaging device 100 includes animage capturing module 202, an image processing module 204, a locationprediction module 206, an illumination module 208, the one or moresensors 132, and the one or more light sources 122. Additionally, theimage processing module 204 includes a face detection module 210, an eyedetection module 212, and a head pose estimation module 214. Further,the location prediction module 206 includes a sensor processing module216 and history data 218. As shown in the illustrative embodiment, theillumination module 208 includes an interval prediction module 220. Eachof the image capturing module 202, the image processing module, thelocation prediction module 206, the illumination module 208, the facedetection module 210, the eye detection module 212, the head poseestimation module 214, the sensor processing module 216, and theinterval prediction module 220 may be embodied as hardware, software,firmware, or a combination thereof. Additionally, in some embodiments,one of the illustrative modules may form a portion of another module(e.g., the eye detection module 212 may form a portion of the facedetection module 210).

The image capturing module 202 controls the camera 120 to capture imageswithin the field of view of the camera 120. As discussed above, thecamera 120 is illustratively configured to operate in a rolling shuttermode. Accordingly, the image capturing module 202 may control theparameters associated with the operation of that mode. For example, theimage capturing module 202 may determine the exposure time for eachsensor line 130 of the camera 120 (i.e., the amount of time between thetime in which a sensor line is reset and the time in which that sensorline is read). In the illustrative embodiment, each sensor line 130 isexposed for the same amount of time on a rolling basis (see, e.g.,exposure time 614 of FIG. 6).

The image processing module 204 receives the images captured with thecamera 120 from the image capturing module 202 (e.g., captured asstreamed video or otherwise as a collection of images/frames). Asdiscussed in more detail below, the image processing module 204 analyzeseach of the images (e.g., each frame of a streamed video or a subsetthereof) to determine the location of an object to be tracked. It shouldbe appreciated that the image processing module 204 may utilize anysuitable object detection/tracking algorithm for doing so. In theillustrative embodiment, the imaging device 100 is used to track auser's eyes using camera and light source synchronization as discussedbelow. However, in other embodiments, the imaging device 100 may be usedto track other features of the user (e.g., head positioning) and/orother objects.

As discussed above, in some embodiments, the imaging device 100 performseye/gaze tracking of one or more persons captured in a scene.Accordingly, in some embodiments, the face detection module 210 maydetect the existence of one or more person's faces in an image anddetermine the location of any detected faces in the captured image.Further, in some embodiments, the face detection module 210 may identifya person based on their detected face (e.g., through biometricalgorithms and/or other face recognition or object correlationalgorithms). As such, in embodiments in which multiple persons aretracked, the face detection module 210 may distinguish between thosepersons in the captured images to enhance tracking quality. Similarly,the eye detection module 212 may detect the location of a person's eyesin the captured image. It should be appreciated that in detecting thelocation of the object (e.g., a person's face and/or eyes), the imageprocessing module 204 or, more specifically, the face detection module210 and/or the eye detection module 212 may determine the sensor lines130 of the camera 120 that correspond with the location of the object inthe image. In doing so, the image processing module 204 may utilize, forexample, predetermined information regarding the number, granularity,size, layout (e.g., horizontal vs. vertical), and/or othercharacteristics of the sensor lines 130. In some embodiments, the eyedetection module 212 utilizes the location of the person's face (i.e.,determined with the face detection module 210) to determine the locationof the person's eyes. Of course, in other embodiments, the eye detectionmodule 212 may make a determination of the location of the person's eyesindependent of or without a determination of the location of theperson's face. The head pose estimation module 214 may determine a headpose of a person based on the determined location of the person's eyesand/or face. As discussed below, the estimated head pose may be used bythe location prediction module 206 (e.g., in conjunction with previoushead pose estimates) to estimate motion and future location of theperson's head within the captured images/video. Further, the imageprocessing module 204 may utilize previous determinations and/orestimations of the face location, eye location, and/or head pose inorder to reduce an area (i.e., a search area) of the captured image toanalyze to determine a face location, eye location, and/or head pose ofthe person in the current image.

The location prediction module 206 estimates the location of the trackedobject (e.g., a person's eyes or face) in the next captured image (e.g.,a subsequent video frame). In some embodiments, the location predictionmodule 206 predicts the next location of the object based on sensor dataand other history data 218. As such, the sensor processing module 216may process data received from the one or more sensors 132. For example,the sensors 132 may include inertial, optical, and/or other sensorsconfigured to detect movement of the imaging device 100, the camera 120,and/or a tracked object (e.g., a person's head, face, or eyes). Thesensor processing module 216 may analyze the sensor data received fromthose sensors 132 using any suitable algorithm. For example, the sensorprocessing module 216 may determine the linear and/or angular motion ofthe camera 120.

The history data 218 may include data identifying previously detected orestimated locations of a person's eyes, face, head pose, or otherobjects/features from analyses of previous captured images. As such, itshould be appreciated that the imaging device 100 may store (e.g., inthe memory 114) detected and/or estimated object locations and otherhistory data 218 for subsequent use. In some embodiments, the locationprediction module 206 fuses, combines, or otherwise analyzes the sensordata in conjunction with the history data 218 to estimate the motionand/or next location of the tracked object. For example, estimates ofthe motion of a person's head and of the motion of the camera 120 may beused in estimating the motion and the next location of the object. Suchanalyses may be used to reduce the portions of the next image requiringanalysis to determine the location of the object. As indicated above,the location of the object within the image corresponds with one or moresensors lines of the camera 120. Accordingly, the location predictionmodule 206 may determine the sensor lines 130 corresponding with theestimated location of the object in the next frame.

The illumination module 208 activates/deactivates the light source(s)122 based on the predicted location of the tracked object in the nextframe. In doing so, the interval prediction module 220 determines anillumination interval during which to activate the one or more lightsources 122 during the capture of the next image based on the predictedlocation of the tracked object in the next image (i.e., based on theanalysis of the location prediction module 206). In the illustrativeembodiment, the illumination interval defines a period of time duringwhich the camera 120 is to expose, in the next captured image, the setof sensor lines 130 (i.e., one or more sensor lines) corresponding withthe predicted location of the tracked object. It should be appreciatedthat, in some embodiments, the sensor lines 130 are constantly exposedwhen they are not being read. However, as used herein, a sensor line 130is considered to be “exposed” during the period of time occurring afterthe particular sensor line 130 has been reset and before the particularsensor line 130 has been read (see, e.g., exposure time 614 of FIG. 6).As such, in the illustrative embodiment, each sensor line 130 has thesame exposure time, albeit occurring at a different absolute time and ona rolling, sequential basis.

As indicated above, the location prediction module 206 may determine thesensor lines 130 corresponding with the predicted location of thetracked object (e.g., a person's eyes) in the next image/frame.Accordingly, the interval prediction module 220 may determine the timeinterval during which those determined sensor lines 130 are scheduled tobe reset and/or read. To do so, in some embodiments, the camera 120 (orthe image capturing module 202) transmits a synchronization signal tothe interval prediction module 220. The interval prediction module 220may utilize the synchronization signal, one or more clocks or triggers(e.g., a pixel clock of the camera 120), parameter data of the camera120 (e.g., exposure time, number of sensor lines, read time per sensorline, total read time, and other parameter data) and/or parameter dataof the light sources (e.g., the onset time of the light source, which isthe time from electrical power up to full illumination power, the timedelay of the power driver, and other parameter data) to determine thetime in which the relevant sensor lines 130 should be read (i.e., theillumination interval). As indicated above, the illumination module 208activates the one or more light sources 122 during the illuminationinterval (see, e.g., illumination interval 616 of FIG. 6) anddeactivates the light sources 122 outside the illumination interval. Ofcourse, in some embodiments, the illumination module 208 may activatethe light sources 122 for an interval greater than the illuminationinterval (e.g., to account for slightly erroneous estimations of thelocation of the object). That is, the light sources 122 may be activatedduring the illumination interval and during a buffer time at thebeginning and/or end of that interval. In some embodiments, the imageprocessing module 204 may analyze the captured image in order todetermine which sensor lines 130 were actually illuminated by the lightsource 122 (e.g., due to delay between sensor line exposure and lightsource 122 illumination). In such embodiments, the imaging device 100may compare the determined, actual illuminated sensor lines 130 to thosesensor lines 130 intended to be illuminated during the capture of theimage. If the difference between the actual and intended illuminatedsensor lines 130 is greater than a reference threshold, the illuminationmodule 208 may modify (i.e., increase or decrease) the delay time of thenext illumination interval to compensate for unknown delays in theimaging device 100.

It should be appreciated that the imaging device 100 may not have anyinformation regarding the location of the tracked object when the firstimage is captured. Accordingly, in some embodiments, the light sources)122 may remain activated while capturing the entirety of the first imageor first few images. The imaging device 100 may analyze those imagesusing the mechanisms described above to determine the location of theobject and estimate the next location of the object. Once the imagingdevice 100 has information regarding an estimated location of the objectin the next image, the imaging device 100 may utilize the mechanismsdescribed herein for camera and light source synchronization. Althoughthe mechanisms described above are described in terms of tracking asingle object, in other embodiments, the camera 120 and light sources122 may be synchronized to track multiple objects. Additionally, inother embodiments, the imaging device 100 may utilize different criteriafor determining when to commence camera and light sourcesynchronization.

Referring now to FIG. 3, in use, the imaging device 100 may execute amethod 300 for camera and light source synchronization. The illustrativemethod 300 begins with block 302 in which the imaging device 100determines whether to track eye movement of a person in the field ofview of the camera 120. Of course, in some embodiments, the imagingdevice 100 may track the movement of other objects. If the imagingdevice 100 determines to track a subject's eye movement, the imagingdevice 100 captures an image of the subject in block 304. As discussedabove, the imaging device 100 may capture video (e.g., in a stream) andanalyze each frame/image (or a portion of the frames) of the capturedvideo.

In block 306, the imaging device 100 determines the location of thesubject's eyes in the captured image. In particular, in someembodiments, the imaging device 100 determines which sensor lines 130 ofthe camera 120 correspond with the location of the subject's eyes in thecaptured image. It should be appreciated that the imaging device 100 mayuse any suitable mechanism or algorithm to determine the location of thesubject's eyes. In doing so, in some embodiments, the imaging device 100determines the location of the subject's face in block 308 as discussedabove. Further, in some embodiments, the imaging device 100 utilizesprevious predictions of the eye location to determine the location ofthe subject's eyes. For example, as discussed above, the imaging device100 may rely on previous predictions/estimations of the location of thesubject's eyes to reduce a search area of the captured image.

In block 312, the imaging device 100 predicts the next location of thesubject's eyes. In other words, the imaging device 100 predicts thelocation of the subject's eyes in the next captured image. In doing so,the imaging device 100 may receive sensor data regarding motion of thecamera 120 and/or the subject. As discussed above, the imaging device100 may utilize the sensor data to provide a more accurate estimation ofthe location of the subject's eyes in the next image. In block 316, theimaging device 100 determines an illumination interval for the nextimage based on the predicted eye location. As discussed above, in someembodiments, the illumination interval defines the period of time duringwhich the camera 120 is to expose the set of sensor lines 130 in thenext captured image corresponding with the predicted location of thesubject's eyes. It should be appreciated that, in block 318, the imagingdevice 100 may determine the exposure interval/time for the sensor lines130 of the camera 120 in doing so. In block 320, the imaging device 100may also determine which sensor lines 130 were actually illuminated bythe light sources 122. As discussed above, the imaging device 100 maycompare the sensor lines 130 actually illuminated to the sensor lines130 intended to be illuminated during the capture of the image. Based onthat analysis, the imaging device 100 may modify the next illuminationinterval (e.g., by incorporating a delay).

In block 322, the imaging device 100 captures the next image of thesubject. In embodiments in which the camera 120 captures video, this mayentail receiving the next image frame of the video. In block 324, theimaging device 100 illuminates the subject during the illuminationinterval with the one or more light sources 122 during the capture ofthe next image. As discussed above, the light sources 122 are activatedwhen the camera 120 is resetting and/or reading the one or more sensorlines 130 corresponding with the prediction location of the subject'seyes. Outside that interval, the light sources 122 may be deactivated toimprove energy efficiency or provide other peripheral benefits asdiscussed above. In block 326, the imaging device 100 determines whetherto continue tracking the subject's eyes. If so, the method 300 returnsto block 306 in which the imaging device 100 determines the location ofthe subject's eyes.

Referring now to FIG. 4, in use, the imaging device 100 may execute amethod 400 for resetting sensor lines with camera and light sourcesynchronization. It should be appreciated that the method 400 may beexecuted in parallel with the method 500 of FIG. 5 (discussed below) forreading sensor lines. The illustrative method 400 begins with block 402in which the imaging device 100 determines whether to capture the nextimage. As discussed above, the camera 120 of the imaging device 100 maycapture each image (e.g., of a video) using a rolling shutter mode.Accordingly, if the next image is to be captured, the imaging device 100determines, in block 404, whether the next sensor line 130 includes thesubject's eyes. As discussed above, in some embodiments, the imagingdevice 100 determines the set of sensor lines 130 corresponding with thepredicted/estimated location of the subject's eyes. As such, the imagingdevice 100 may compare that set of sensor lines 130 with the next sensorline 130 to determine whether the next sensor line 130 includes aportion of the subject's eyes.

If so, the imaging device 100 determines, in block 406, whether theillumination (e.g., via the light sources 122) is already activated. Insome embodiments, the illumination should only be already activated ifthe previously reset sensor line 130 includes the subject's eyes. If theillumination is not already activated, the imaging device 100 activatesthe illumination in block 408. That is, the imaging device 100 turns onthe one or more light sources 122 to illuminate the subject's eyes. Inblock 410, the imaging device 100 resets the next sensor line 130 (i.e.,with the camera 120). Additionally, if the imaging device 100determines, in block 404, that the next sensor line 130 does not includethe subject's eyes or, in block 406, that the illumination is alreadyactivated, the method 400 advances to block 410 in which the imagingdevice 100 resets the next sensor line. It should be appreciated that,in some embodiments, the imaging device 100 may activate the lightsources 122 and reset the next sensor line 130 contemporaneously or inreverse order to that shown in FIG. 4 and described herein.

In block 412, the imaging device 100 may initialize an exposure timerfor the next sensor line 130 (e.g., the first reset sensor line). Inother embodiments, the imaging device 100 may receive a synchronizationsignal or other temporal data from the camera 120 regarding theresetting/reading schedule and/or other parameters of the camera 120 Asdiscussed above, in the illustrative embodiment, each of the sensorlines 130 is exposed for the same amount of time on a rolling,sequential basis. In some embodiments, an exposure timer is set based onthe exposure time established by the imaging device 100 or the camera120 upon resetting the first sensor line. Expiration of the exposuretimer indicates that the first sensor line 130 has reached the desiredexposure time. Accordingly, in some embodiments, the camera 120 readsthe first sensor line 130 after expiration of the exposure timer and,thereafter, consecutively reads the remaining sensor lines 130 in theorder in which they have been reset (see FIG. 6). As such, it should beappreciated that a sensor line 130 being read at a particular time isone that was reset a certain time ago defined by the duration of theexposure time. In other embodiments, an exposure timer may beindependently set for each sensor line 130. In block 414, the imagingdevice 100 determines whether there are any other sensor lines 130 inthe next image that have not been reset. If so, the method 400 returnsto block 404 in which the imaging device 100 determines whether the nextsensor line 130 includes the subject's eyes. In other words, the imagingdevice 100 sequentially resets the sensor lines 130 of the camera 120and activates or maintains illumination during periods of time in whichthe imaging device 100 is resetting sensor lines 130 corresponding withthe location of the subject's eyes in the image.

Referring now to FIG. 5, in use, the imaging device 100 may execute amethod 500 for reading sensor lines with camera and light sourcesynchronization. As indicated above, the method 500 may be executed inparallel with the method 400 of FIG. 4. The illustrative method 500begins with block 502 in which the imaging device 100 determines whetherthe exposure time for the next sensor line 130 has elapsed. As discussedabove with regard to method 400 of FIG. 4, an exposure timer orsynchronization signal may be utilized to determine when to read thefirst sensor line 130 and/or subsequent sensor lines.

If the next sensor line 130 has been exposed for the determined amountof time (i.e., the exposure time), the imaging device 100 determineswhether the next sensor line 130 includes the subject's eyes in block504. If not, the imaging device 100 determines, in block 506, whetherthe last sensor line 130 read (i.e., by the camera 120) included thesubject's eyes. For example, suppose the sensor lines 130 are readsequentially such that, without loss of generality, line 1 is readfirst, line 2 is read second, line 3 is read third, and so on. Further,suppose that the next sensor line 130 to be read is line 2. In such anexample, the imaging device 100 determines whether line 1, which hasbeen previously read, included the subject's eyes. In some embodiments,the imaging device 100 does not analyze line 1 to make such adetermination but, instead, relies on a previous estimation/predictionof the location of the subject's eyes as discussed above. For example,the imaging device 100 may compare the set of sensor lines 130corresponding with the predicted/estimated location of the subject'seyes with line 1 (e.g., by comparing the line numbers/identifiers). Ofcourse, once the image is captured in full or part, the imaging device100 may analyze the captured image or portion thereof to determine theactual location of the subject's eyes in the image and predict the nextlocation of the subject's eyes.

If the next sensor line 130 does not include the subject's eyes and thelast sensor line 130 read included the subject's eyes, the imagingdevice 100 deactivates illumination in block 508. That is, the imagingdevice 100 turns off one or more of the light sources 122 activated inblock 408 of FIG. 4. In block 510, the imaging device 100 reads the nextsensor line 130 (i.e., with the camera 120). Additionally, if theimaging device 100 determines, in block 504, that the next sensor line130 includes the subject's eyes or, in block 506, that the last sensorline 130 read does not include the subject's eyes, the method 500advances to block 510 in which the imaging device 100 reads the nextsensor line. It should be appreciated that, in some embodiments, theimaging device 100 may deactivate the light sources 122 and read thenext sensor line contemporaneously or in reverse order to that shown inFIG. 5 and described herein. In other words, the light sources 122 mayremain activated until the last sensor line 130 in the set of sensorlines 130 corresponding with the location of the subject's eyes has beenread.

In block 512, the imaging device 100 determines whether there are anyother sensor lines 130 in the next image that have not been read. If so,the method 500 returns to block 502 in which the imaging device 100determines whether the exposure time for the next sensor line 130 haselapsed. As discussed above, in some embodiments, an exposure timer ismonitored only prior to reading the first sensor line 130 and,subsequently, the sensor lines 130 may be read in the same order andfrequency in which they were reset. In other words, the sensor lines 130are reset and read at the same rate, but the reads are delayed by theexposure time (e.g., a static predetermined value) with respect to theresets.

Referring now to FIG. 6, a simplified temporal graph 600 of anembodiment of camera and light source synchronization on the imagingdevice 100 is shown. In the illustrative embodiment, the temporal graph600 shows the temporal arrangement and relationship between theresetting of sensor lines, reading of sensor lines, and illumination ofobjects. The temporal graph 600 shows a coordinate system includingsensor line axis 602 and a time axis 604. Although the graph 600 isshown as a continuous analog system for simplicity, in some embodiments,there is a finite number of sensor lines 130 in the camera 120 (e.g., adigital camera). In the illustrative embodiment, reset times and readtimes for the sensor lines 130 of the camera 120 and associated withthree consecutively captured images are shown. More specifically, thefirst image includes a reset time 606A and a read time 608A; a secondimage includes a reset time 606B and a read time 608B; and a third imageincludes a reset time 606C and a read time 608C.

The illustrative embodiment also shows a first boundary 610 and a secondboundary 612 of the tracked object (e.g., a subject's eyes). In someembodiments, the boundaries 610, 612 denote boundaries of the predictedlocation of the object. As shown in the graph 600, the object movedtoward sensor lines 130 having lower values as time goes on, which isdescribed as being “lower” in the captured image without loss ofgenerality. For example, the object is lower in the captured imagecorresponding with the read time 608C than in the captured imagecorresponding with the read time 608A. An exposure time 614 between thereset time 606C and the read time 608C is also shown for illustrativepurposes. As discussed above, the exposure time is the interval duringwhich a sensor line 130 is exposed and defined by the length of timebetween the reset time and the read time of the sensor line 130. Itshould be appreciated that, as discussed above and illustrated in FIG.6, the exposure time is the same duration, albeit occurring at adifferent absolute time, for each sensor line 130 of each capturedimage. Further, the exposure time may be a predefined parameter of thecamera 120 in some embodiments. In the illustrative embodiment, anillumination interval 616 for the capture of the image correspondingwith the read time 608A is also shown. As discussed above and shown inFIG. 6, the illumination interval defines the period of time duringwhich the camera 120 is to expose the set of sensor lines 130corresponding with the predicted location of the tracked object.

Examples

Illustrative examples of the technologies disclosed herein are providedbelow. An embodiment of the technologies may include any one or more,and any combination of, the examples described below.

Example 1 includes an imaging device for camera and light sourcesynchronization, the imaging device comprising an image processingmodule to detect a current location of an object in a captured imagegenerated by the imaging device; a location prediction module to predicta next location of the object in a next captured image, generated by theimaging device, based on the current location of the object; and anillumination module to (i) determine an illumination interval defining aperiod of time during which a camera of the imaging device is to exposea set of sensor lines during the capture of the next captured image,wherein the set of sensor lines corresponds with the predicted nextlocation of the object and (ii) activate a light source of the imagingdevice to illuminate the object throughout the determined illuminationinterval.

Example 2 includes the subject matter of Example 1, and wherein todetect the current location of the object comprises to detect a currentlocation of a subject's eyes in the captured image.

Example 3 includes the subject matter of any of Examples 1 and 2, andwherein to detect the current location of the subject's eyes comprisesto detect a current location of the subject's face in the capturedimage.

Example 4 includes the subject matter of any of Examples 1-3, andwherein to detect the current location of the object comprises to reducea search area of the captured image based on a previously predictedlocation of the object.

Example 5 includes the subject matter of any of Examples 1-4, andwherein the location prediction module is to receive sensor dataindicative of motion of the computing device or the object, wherein topredict the next location of the object comprises to predict a nextlocation of the object in the next captured image based on the currentlocation and the sensor data.

Example 6 includes the subject matter of any of Examples 1-5, andfurther including at least one sensor to generate the sensor data.

Example 7 includes the subject matter of any of Examples 1-6, andwherein to predict the next location of the object comprises to predicta next location of the object in the next captured image based on thecurrent location and a previously detected location of the object in apreviously captured image.

Example 8 includes the subject matter of any of Examples 1-7, andwherein the illumination module is to deactivate the light source duringa period of time outside the determined illumination interval in whichthe camera is to expose the set of sensor lines of the next capturedimage.

Example 9 includes the subject matter of any of Examples 1-8, andfurther including an image capturing module to capture the next capturedimage with the camera of the imaging device.

Example 10 includes the subject matter of any of Examples 1-9, andwherein the camera is to capture the next captured image based on anelectronic rolling shutter mode.

Example 11 includes the subject matter of any of Examples 1-10, andwherein the set of sensor lines corresponding with the predicted nextlocation of the object comprises a single sensor line.

Example 12 includes the subject matter of any of Examples 1-11, andwherein the imaging device is one of a tablet computer, a laptopcomputer, or a cellular phone.

Example 13 includes the subject matter of any of Examples 1-12, andfurther including an image capturing module to sequentially reset eachsensor line in the next captured image, wherein the illumination moduleis to activate the light source in response to a determination that (i)the next sensor line to be reset corresponds with the predicted nextlocation of the object and (ii) the light source is not alreadyactivated.

Example 14 includes the subject matter of any of Examples 1-13, andwherein the image capturing module is to sequentially read each sensorline in the next captured image a predetermined exposure time after eachsensor line is sequentially reset; and wherein the illumination moduleis to deactivate the light source in response to a determination thatneither the next sensor line to be read nor the last sensor line readcorresponds with the predicted next location of the object.

Example 15 includes the subject matter of any of Examples 1-14, andwherein the image processing module is to analyze the next capturedimage to identify illuminated sensor lines indicative of the sensorlines illuminated during the capture of the next captured image; andwherein the illumination module is to adjust the illumination intervalbased on the analysis of the image processing module.

Example 16 includes a method for camera and light source synchronizationon an imaging device, the method comprising detecting, by the imagingdevice, a current location of an object in a captured image generated bythe imaging device; predicting, by the imaging device, a next locationof the object in a next captured image, generated by the imaging device,based on the current location of the object; determining, by the imagingdevice, an illumination interval defining a period of time during whicha camera of the imaging device is to expose a set of sensor lines duringthe capturing of the next captured image, the set of sensor linescorresponding with the predicted next location of the object; andactivate, by the imaging device, a light source of the imaging device toilluminate the object during the determined illumination interval.

Example 17 includes the subject matter of Example 16, and whereindetecting the current location of the object comprises detecting acurrent location of the subject's eyes in the captured image.

Example 18 includes the subject matter of any of Example 16 and 17, andwherein detecting the current location of the subject's eyes comprisesdetecting a current location of the subject's face in the capturedimage.

Example 19 includes the subject matter of any of Example 16-18, andwherein detecting the current location of the object comprises reducinga search area of the captured image based on a previously predictedlocation of the object.

Example 20 includes the subject matter of any of Example 16-19, andfurther including receiving, with the imaging device, sensor dataindicating any motion of the imaging device or the object, whereinpredicting the next location of the object comprises predicting a nextlocation of the object in the next captured image based on the currentlocation and the sensor data.

Example 21 includes the subject matter of any of Example 16-20, andwherein predicting the next location of the object comprises predictinga next location of the object in the next captured image based on thecurrent location and a previously detected location of the object in apreviously captured image.

Example 22 includes the subject matter of any of Example 16-21, andfurther including deactivating, by the imaging device, the light sourceduring a period of time outside the determined illumination interval inwhich the camera is to expose the set of sensor lines of the nextcaptured image.

Example 23 includes the subject matter of any of Example 16-22, andfurther including capturing, by the camera of the imaging device, thenext captured image.

Example 24 includes the subject matter of any of Example 16-23, andwherein capturing the next captured image comprises using an electronicrolling shutter of the camera.

Example 25 includes the subject matter of any of Example 16-24, andwherein the set of sensor lines corresponding with the predicted nextlocation of the object comprises a single sensor line.

Example 26 includes the subject matter of any of Example 16-25, andwherein the imaging device is one of a tablet computer, a laptopcomputer, or a cellular phone.

Example 27 includes the subject matter of any of Example 16-26, andfurther including resetting, sequentially by the imaging device, eachsensor line in the next captured image; and activating, by the imagingdevice, the light source in response to determining that (i) the nextsensor line to be reset corresponds with the predicted next location ofthe object and (ii) the light source is not already activated.

Example 28 includes the subject matter of any of Example 16-27, andfurther including reading, sequentially by the imaging device, eachsensor line in the next captured image a predetermined exposure timeafter each sensor line is sequentially reset; and deactivating, by theimaging device, the light source in response to determining that neitherthe next sensor line to be read nor the last sensor line readcorresponds with the predicted next location of the object.

Example 29 includes the subject matter of any of Example 16-28, andfurther including analyzing, by the imaging device, the next capturedimage to identify illuminated sensor lines indicative of the sensorlines illuminated during the capture of the next captured image; andadjusting, by the imaging device, the illumination interval based on theanalysis of the next captured image.

Example 30 includes a computing device comprising a processor; and amemory having stored therein a plurality of instructions that whenexecuted by the processor cause the computing device to perform themethod of any of Examples 16-29.

Example 31 includes one or more machine-readable storage mediacomprising a plurality of instructions stored thereon that, in responseto being executed, result in a computing device performing the method ofany of Examples 16-29.

Example 32 includes a computing device for camera and light sourcesynchronization, the computing device comprising means for detecting acurrent location of an object in a captured image generated by thecomputing device; means for predicting a next location of the object ina next captured image, generated by the computing device, based on thecurrent location of the object; means for determining an illuminationinterval defining a period of time during which a camera of thecomputing device is to expose a set of sensor lines during the capturingof the next captured image, the set of sensor lines corresponding withthe predicted next location of the object; and means for activating alight source of the computing device to illuminate the object during thedetermined illumination interval.

Example 33 includes the subject matter of Example 32, and wherein themeans for detecting the current location of the object comprises meansfor detecting a current location of the subject's eyes in the capturedimage.

Example 34 includes the subject matter of any of Examples 32 and 33, andwherein the means for detecting the current location of the subject'seyes comprises means for detecting a current location of the subject'sface in the captured image.

Example 35 includes the subject matter of any of Examples 32-34, andwherein the means for detecting the current location of the objectcomprises means for reducing a search area of the captured image basedon a previously predicted location of the object.

Example 36 includes the subject matter of any of Examples 32-35, andfurther including means for receiving sensor data indicating any motionof the computing device or the object, wherein the means for predictingthe next location of the object comprises means for predicting a nextlocation of the object in the next captured image based on the currentlocation and the sensor data.

Example 37 includes the subject matter of any of Examples 32-36, andwherein the means for predicting the next location of the objectcomprises means for predicting a next location of the object in the nextcaptured image based on the current location and a previously detectedlocation of the object in a previously captured image.

Example 38 includes the subject matter of any of Examples 32-37, andfurther including means for deactivating the light source during aperiod of time outside the determined illumination interval in which thecamera is to expose the set of sensor lines of the next captured image.

Example 39 includes the subject matter of any of Examples 32-38, andfurther including means for capturing, by the camera of the computingdevice, the next captured image.

Example 40 includes the subject matter of any of Examples 32-39, andwherein the means for capturing the next captured image comprises meansfor using an electronic rolling shutter of the camera.

Example 41 includes the subject matter of any of Examples 32-40, andwherein the set of sensor lines corresponding with the predicted nextlocation of the object comprises a single sensor line.

Example 42 includes the subject matter of any of Examples 32-41, andwherein the computing device is one of a tablet computer, a laptopcomputer, or a cellular phone.

Example 43 includes the subject matter of any of Examples 32-42, andfurther including means for resetting, sequentially by the computingdevice, each sensor line in the next captured image; and means foractivating the light source in response to a determination that (i) thenext sensor line to be reset corresponds with the predicted nextlocation of the object and (ii) the light source is not alreadyactivated.

Example 44 includes the subject matter of any of Examples 32-43, andfurther including means for reading, sequentially by the computingdevice, each sensor line in the next captured image a predeterminedexposure time after each sensor line is sequentially reset; and meansfor deactivating the light source in response to a determination thatneither the next sensor line to be read nor the last sensor line readcorresponds with the predicted next location of the object.

Example 45 includes the subject matter of any of Examples 32-44, andfurther including means for analyzing the next captured image toidentify illuminated sensor lines indicative of the sensor linesilluminated during the capture of the next captured image; and means foradjusting the illumination interval based on the analysis of the nextcaptured image.

1-25. (canceled)
 26. An imaging device for camera and light sourcesynchronization, the imaging device comprising: an image processingmodule to detect a current location of an object in a captured imagegenerated by the imaging device; a location prediction module to predicta next location of the object in a next captured image, generated by theimaging device, based on the current location of the object; and anillumination module to (i) determine an illumination interval defining aperiod of time during which a camera of the imaging device is to exposea set of sensor lines during the capture of the next captured image,wherein the set of sensor lines corresponds with the predicted nextlocation of the object and (ii) activate a light source of the imagingdevice to illuminate the object throughout the determined illuminationinterval.
 27. The imaging device of claim 26, wherein to detect thecurrent location of the object comprises to detect a current location ofa subject's eyes in the captured image.
 28. The imaging device of claim26, wherein to detect the current location of the object comprises toreduce a search area of the captured image based on a previouslypredicted location of the object.
 29. The imaging device of claim 26,wherein the location prediction module is to receive sensor dataindicative of motion of the computing device or the object, wherein topredict the next location of the object comprises to predict a nextlocation of the object in the next captured image based on the currentlocation and the sensor data.
 30. The imaging device of claim 26,wherein to predict the next location of the object comprises to predicta next location of the object in the next captured image based on thecurrent location and a previously detected location of the object in apreviously captured image.
 31. The imaging device of claim 26, whereinthe illumination module is to deactivate the light source during aperiod of time outside the determined illumination interval in which thecamera is to expose the set of sensor lines of the next captured image.32. The imaging device of claim 26, further comprising an imagecapturing module to capture the next captured image with the camera ofthe imaging device, wherein the camera is to capture the next capturedimage based on an electronic rolling shutter mode.
 33. The imagingdevice of claim 26, wherein the imaging device is one of a tabletcomputer, a laptop computer, or a cellular phone.
 34. The imaging deviceof claim 26, further comprising an image capturing module tosequentially reset each sensor line in the next captured image, whereinthe illumination module is to activate the light source in response to adetermination that (i) the next sensor line to be reset corresponds withthe predicted next location of the object and (ii) the light source isnot already activated.
 35. The imaging device of claim 34, wherein theimage capturing module is to sequentially read each sensor line in thenext captured image a predetermined exposure time after each sensor lineis sequentially reset; and wherein the illumination module is todeactivate the light source in response to a determination that neitherthe next sensor line to be read nor the last sensor line readcorresponds with the predicted next location of the object.
 36. Theimaging device of claim 26, wherein the image processing module is toanalyze the next captured image to identify illuminated sensor linesindicative of the sensor lines illuminated during the capture of thenext captured image; and wherein the illumination module is to adjustthe illumination interval based on the analysis of the image processingmodule.
 37. One or more machine-readable storage media comprising aplurality of instructions stored thereon that, in response to executionby an imaging device, cause the imaging device to: detect a currentlocation of an object in a captured image generated by the imagingdevice; predict a next location of the object in a next captured image,generated by the imaging device, based on the current location of theobject; determine an illumination interval defining a period of timeduring which a camera of the imaging device is to expose a set of sensorlines during the capturing of the next captured image, the set of sensorlines corresponding with the predicted next location of the object; andactivate a light source of the imaging device to illuminate the objectduring the determined illumination interval.
 38. The one or moremachine-readable storage media of claim 37, wherein to detect thecurrent location of the object comprises to detect a current location ofthe subject's eyes in the captured image.
 39. The one or moremachine-readable storage media of claim 38, wherein to detect thecurrent location of the subject's eyes comprises to detect a currentlocation of the subject's face in the captured image.
 40. The one ormore machine-readable storage media of claim 37, wherein to detect thecurrent location of the object comprises to reduce a search area of thecaptured image based on a previously predicted location of the object.41. The one or more machine-readable storage media of claim 37, whereinthe plurality of instructions further cause the imaging device toreceive sensor data that indicates any motion of the imaging device orthe object, wherein to predict the next location of the object comprisesto predict a next location of the object in the next captured imagebased on the current location and the sensor data.
 42. The one or moremachine-readable storage media of claim 37, wherein to predict the nextlocation of the object comprises to predict a next location of theobject in the next captured image based on the current location and apreviously detected location of the object in a previously capturedimage.
 43. The one or more machine-readable storage media of claim 37,wherein the plurality of instructions further cause the imaging deviceto deactivate the light source during a period of time outside thedetermined illumination interval in which the camera is to expose theset of sensor lines of the next captured image.
 44. The one or moremachine-readable storage media of claim 37, wherein the plurality ofinstructions further cause the imaging device to: reset, sequentially,each sensor line in the next captured image; and activate the lightsource in response to a determination that (i) the next sensor line tobe reset corresponds with the predicted next location of the object and(ii) the light source is not already activated.
 45. The one or moremachine-readable storage media of claim 44, wherein the plurality ofinstructions further cause the imaging device to: read, sequentially,each sensor line in the next captured image a predetermined exposuretime after each sensor line is sequentially reset; and deactivate thelight source in response to a determination that neither the next sensorline to be read nor the last sensor line read corresponds with thepredicted next location of the object.
 46. The one or moremachine-readable storage media of claim 37, wherein the plurality ofinstructions further cause the imaging device to: analyze the nextcaptured image to identify illuminated sensor lines indicative of thesensor lines illuminated during the capture of the next captured image;and adjust the illumination interval based on the analysis of the nextcaptured image.
 47. A method for camera and light source synchronizationon an imaging device, the method comprising: detecting, by the imagingdevice, a current location of an object in a captured image generated bythe imaging device; predicting, by the imaging device, a next locationof the object in a next captured image, generated by the imaging device,based on the current location of the object; determining, by the imagingdevice, an illumination interval defining a period of time during whicha camera of the imaging device is to expose a set of sensor lines duringthe capturing of the next captured image, the set of sensor linescorresponding with the predicted next location of the object; andactivate, by the imaging device, a light source of the imaging device toilluminate the object during the determined illumination interval. 48.The method of claim 47, further comprising: resetting, sequentially bythe imaging device, each sensor line in the next captured image; andactivating, by the imaging device, the light source in response todetermining that (i) the next sensor line to be reset corresponds withthe predicted next location of the object and (ii) the light source isnot already activated.
 49. The method of claim 48, further comprising:reading, sequentially by the imaging device, each sensor line in thenext captured image a predetermined exposure time after each sensor lineis sequentially reset; and deactivating, by the imaging device, thelight source in response to determining that neither the next sensorline to be read nor the last sensor line read corresponds with thepredicted next location of the object.
 50. The method of claim 47,further comprising: analyzing, by the imaging device, the next capturedimage to identify illuminated sensor lines indicative of the sensorlines illuminated during the capture of the next captured image; andadjusting, by the imaging device, the illumination interval based on theanalysis of the next captured image.